Map and ablate open irrigated hybrid catheter

ABSTRACT

An embodiment of an open-irrigated catheter system comprises a tip section, a distal insert, and mapping electrodes. The tip section has an exterior wall that defines an open interior region within the tip section. The exterior wall includes mapping electrode openings and irrigation ports. The exterior wall is conductive for delivering radio frequency (RF) energy for an RF ablation procedure. The irrigation ports are in fluid communication with the open interior region to allow fluid to flow from the open interior region through the irrigation ports. The distal insert is positioned within the tip section to separate the open region into a distal fluid reservoir and a proximal fluid reservoir. The mapping electrodes are positioned in the mapping electrode openings in the tip section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/859,523, filed Apr. 9, 2013, now U.S. Pat. No. 8,740,900; which is acontinuation of U.S. application Ser. No. 12/821,459, filed Jun. 23,2010, now U.S. Pat. No. 8,414,579; which claims the benefit of U.S.Provisional Application No. 61/325,456, filed on Apr. 19, 2010 and U.S.Provisional Application No. 61/221,967, filed on Jun 30, 2009, under 35U.S.C. §119(e), the entire disclosures of which are incorporated hereinby reference.

TECHNICAL FIELD

This application relates generally to medical devices and, moreparticularly, to systems, devices and methods related to open-irrigatedhybrid catheters used to perform mapping and ablation functions.

BACKGROUND

Aberrant conductive pathways disrupt the normal path of the heart'selectrical impulses. For example, conduction blocks can cause theelectrical impulse to degenerate into several circular wavelets thatdisrupt the normal activation of the atria or ventricles. The aberrantconductive pathways create abnormal, irregular, and sometimeslife-threatening heart rhythms called arrhythmias. Ablation is one wayof treating arrhythmias and restoring normal contraction. The sources ofthe aberrant pathways (called focal arrhythmia substrates) are locatedor mapped using mapping electrodes situated in a desired location. Aftermapping, the physician may ablate the aberrant tissue. In radiofrequency (RF) ablation, RF energy is directed from the ablationelectrode through tissue to an electrode to ablate the tissue and form alesion.

SUMMARY

An embodiment of an open-irrigated catheter system comprises a tipsection, a distal insert, and mapping electrodes. The tip section has anexterior wall that defines an open interior region within the tipsection. The exterior wall includes mapping electrode openings andirrigation ports. The exterior wall is conductive for delivering radiofrequency (RF) energy for an RF ablation procedure. The irrigation portsare in fluid communication with the open interior region to allow fluidto flow from the open interior region through the irrigation ports. Thedistal insert is positioned within the tip section to separate the openregion into a distal fluid reservoir and a proximal fluid reservoir. Themapping electrodes are positioned in the mapping electrode openings inthe tip section.

A catheter system embodiment comprises a conductive exterior wall withmapping electrode openings, wherein the conductive exterior wall isconfigured for use in delivering RF energy for ablation functions. Thecatheter system embodiment may, but need not, be an open-irrigatedcatheter. The catheter system embodiment includes mapping electrodespositioned in the mapping electrode openings, and noise artifactisolators positioned in the mapping electrode openings. The mappingelectrodes are electrically insulated from the exterior wall by thenoise artifact isolators.

An electrode assembly embodiment comprises an electrode, an electrodeshaft, and a noise artifact isolator. The electrode has a circumferencedefining sides of the electrode, a first surface, and a second surfaceopposite the first surface. The electrode shaft extends from the secondsurface of the electrode, and is in electrical conduction with theelectrode. The noise artifact isolator is in contact with the sides ofthe electrode and surrounds the circumference of the electrode.

A method of forming an open-irrigated catheter tip includes inserting adistal insert into a distal tip section and connecting the distal tipsection to a proximally adjacent structure. Inserting the distal insertincludes moving the distal insert into the distal tip section until adistal extension of the insert contacts a distal end of the distal tipsection to self-position the distal insert proximate to irrigationports.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive treatmentof the present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Thescope of the present invention is defined by the appended claims andtheir equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are illustrated by way of example in the figures ofthe accompanying drawings. Such embodiments are demonstrative and notintended to be exhaustive or exclusive embodiments of the presentsubject matter.

FIGS. 1A-1D illustrate an embodiment of a hybrid catheter with distalirrigation ports and three microelectrodes used to perform the mappingfunction.

FIGS. 2A-2D illustrate an embodiment of a hybrid catheter with distalirrigation ports and four microelectrodes used to perform the mappingfunction.

FIGS. 3A-3D illustrate a microelectrode with a noise artifact isolator,according to various embodiments.

FIGS. 4A-4C illustrate an embodiment of a hybrid catheter in which thetip body includes separate distal and proximal portions, and where boththe distal and proximal portions of the tip body are configured toconnect to the distal insert that separates the distal and proximalportions.

FIGS. 5A-5D illustrate an embodiment of a map and ablate catheter withdistal and proximal irrigation ports.

FIGS. 6A-6B illustrate an embodiment of a map and ablate catheter withdistal irrigation ports.

FIGS. 7A-7B illustrate another embodiment of a map and ablate catheterwith distal irrigation ports and a proximal fluid chamber.

FIGS. 8A-8C illustrate various distal insert embodiments configured forself-alignment and configured to isolate electrical components from theirrigation fluid.

FIGS. 9A-9C illustrate various embodiments for realizing a seal areabetween the distal inserts and the exterior wall of the electrode tip.

FIG. 10 illustrates a section view of a tip electrode assemblyembodiment that includes an embodiment of a distal insert.

FIG. 11 illustrates an embodiment of a mapping and ablation system thatincludes an open-irrigated catheter.

DETAILED DESCRIPTION

The following detailed description of the present invention refers tosubject matter in the accompanying drawings which show, by way ofillustration, specific aspects and embodiments in which the presentsubject matter may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresent subject matter. References to “an,” “one,” or “various”embodiments in this disclosure are not necessarily to the sameembodiment, and such references contemplate more than one embodiment.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope is defined only by the appended claims,along with the full scope of legal equivalents to which such claims areentitled.

This present subject matter generally relates to a radiofrequency (RF)ablation catheter system. The catheter is referred to as a hybridcatheter herein as it can be used simultaneously for both localizedmapping and ablation functions. The hybrid catheter is configured toprovide localized, high resolution ECG signals during ablation. Thelocalized mapping enables the mapping to be more precise than that whichcan be achieved with conventional ablation catheters. The hybridcatheter has an open-irrigated catheter design. A cooling fluid, such asa saline, is delivered through the catheter to the catheter tip, wherethe fluid exits through irrigation ports to cool the electrode andsurrounding tissue. Clinical benefits of such a catheter include, butare not limited to, controlling the temperature and reducing coagulumformation on the tip of the catheter, preventing impedance rise oftissue in contact with the catheter tip, and maximizing potential energytransfer to the tissue. Additionally, the localized intra cardiacelectrical activity can be recorded in real time or near-real time rightat the point of energy delivery.

FIGS. 1A-1D illustrate an embodiment of a hybrid catheter with distalirrigation ports and three microelectrodes used to perform the mappingfunction. The illustrated catheter 100 includes a catheter tip body 101,an open-irrigated tip section 102 used to perform mapping and ablationfunctions, and mapping electrodes 103. With reference to FIG. 1B, theillustrated embodiment includes a generally hollow tip body and a distalinsert 104 disposed therein and configured to separate a proximal fluidreservoir 105 and distal fluid reservoir 106. The hollow tip body has anopen interior region defined by an exterior wall of the tip section.Fluid flow through these reservoirs is used to provide targeted coolingof portions of the tip electrode. In the illustrated embodiment, thehollow tip body has a generally cylindrical shape. By way of an exampleand not limitation, an embodiment of tip body has a diameter on theorder of about 0.08-0.1 inches, has a length on the order of about0.2-0.3 inches, and has an exterior wall with a thickness on the orderof 0.003-0.004 inches.

The illustrated distal insert 104 includes openings or apertures 107sized to receive a microelectrode and its corresponding noise artifactisolator 108. These microelectrodes used in the mapping function toimage localized intra cardiac activity. The device may be used to recordhigh resolution, precise localized electrical activity, to preventexcessive heating of the ablation electrode, to allow greater deliveryof power, to prevent the formation of coagulum and to provide theability to diagnose complex ECG activity. The illustrated distal insert104 also includes a fluid conduit or passage 109 to permit fluid to flowfor the proximal fluid reservoir 105 to the distal fluid reservoir 106,a thermocouple opening 110 sized to receive a thermocouple 111, andopenings 112 sized to receive electrical conductors 113 used to provideelectrical connections to the microelectrodes 103. Also illustrated is athermocouple wire 114 connected to the thermocouple 111. By way ofexample and not limitation, an embodiment of the distal insert isfabricated from stainless steel.

The tip section 102 is formed from a conductive material. For example,some embodiments use a platinum-iridium alloy. Some embodiments use analloy with approximately 90% platinum and 10% iridium. This conductivematerial is used to conduct RF energy used to form legions during theablation procedure. A plurality of irrigation ports 115 or exit portsare shown near the distal end of the tip section 102. By way of exampleand not limitation, an embodiment has irrigation ports with a diameterapproximately within a range of 0.01 to 0.02 inches. Fluid, such as asaline solution, flows from the distal fluid reservoir 106, throughthese ports 115, to the exterior of the catheter. This fluid is used tocool the ablation electrode tip and the tissue near the electrode. Thistemperature control reduces coagulum formation on the tip of thecatheter, prevents impedance rise of tissue in contact with the cathetertip, and increases energy transfer to the tissue because of the lowertissue impedance.

FIGS. 1A-1D illustrate a three microelectrode embodiment in which thethree microelectrodes are used to perform mapping functions. However,the hybrid catheter may include other numbers of microelectrodes. Forexample, FIGS. 2A-2D illustrate an embodiment of a hybrid catheter withdistal irrigation ports and four microelectrodes used to perform themapping function.

The illustrated catheter 200 includes a catheter tip body 201, anopen-irrigated tip section 202 used to perform mapping and ablationfunctions, and microelectrodes 203. With reference to FIG. 1B, theillustrated embodiment includes a generally hollow tip body and a distalinsert 204 disposed therein and configured to separate a proximal fluidreservoir 205 and distal fluid reservoir 206. The illustrated distalinsert 204 includes openings or apertures 207 sized to receive amicroelectrode and its corresponding noise artifact isolator 208. Theillustrated distal insert 204 also includes a fluid conduit or passage209 to permit fluid to flow from the proximal fluid reservoir 205 to thedistal fluid reservoir 206, a thermocouple opening 210 sized to receivea thermocouple 211, and openings 212 sized to receive electricalconductors 213 used to provide electrical connections to themicroelectrodes 203. Also illustrated is a thermocouple wire 214connected to the thermocouple 211.

FIGS. 3A-3D illustrate a microelectrode with a noise artifact isolator,according to various embodiments. The illustrated microelectrode 303 issurrounded by the noise artifact isolator 308. An electrode shaft 315 isconnected to the electrode 303, and provides an electrical connectionbetween the electrode and the electrical conductors. The microelectrodesare small, independent diagnostic sensing electrodes embedded within thewalls of the ablation tip of the RF ablation catheter. The noiseartifact isolator electrically isolates the small electrodes from theconductive walls of the ablation tip. According to various embodiments,the noise artifact isolator is a polymer-based material sleeve and/oradhesive that encapsulates the microelectrodes. The isolator has a lip316 over the outside edge of the microelectrode circumference thatblocks the RF pathway into the surface of the microelectrodes. Accordingto various embodiments, the lip extends a distance within a range ofapproximately 0.002 to 0.020 inches past the surface of the electrode.According to various embodiments, the lip extends a distance ofapproximately 0.003 inches around the circumference of themicroelectrode. The isolator isolates the noise entrance creating a muchcleaner electrogram during an RF ablation mode. An in-vitro test resultprovides evidence that the illustrated isolator significantly reduce thenoise artifact during RF. These electrically-isolated microelectrodesare able to sense highly localized electrical activity, avoid a farfield component, and simultaneously achieve the ability to ablate tissuewithout noise artifact during RF mode.

FIGS. 4A-4C illustrate an embodiment of a hybrid catheter in which thetip body includes separate distal and proximal portions, and where boththe distal and proximal portions of the tip body are configured toconnect to the distal insert that separates the distal and proximalportions. The embodiment illustrated in FIGS. 4A-4C provides a design tosimplify manufacturing of the open-irrigated, mapping and ablationcatheter.

The illustrated device has a distal and proximal chamber separated intoproximal 417 and distal tip sections 418. These sections are separatedby the distal insert 419, which accommodates microelectrodes 420, acooling flow channel 421, and a thermocouple slot 422. The illustrateddistal insert 419 includes openings or apertures 424 sized to receive amicroelectrode and its corresponding noise artifact isolator 423, andopenings 424 sized to receive electrical conductors 425 used to provideelectrical connections to the microelectrodes 420. The distal tip hasdistal holes or irrigations ports 415 around the proximal edge of thedomed section of the tip.

The illustrated distal insert has ends with distal and proximal lipedges 470D and 470P. Both the distal and proximal tip sections 418 and417 are designed to fit over the lip edges of the distal insert ends.Specifically, a proximal side 471 of the distal tip section fits overthe distal lip 470D and a distal side 472 of the proximal section fitsover the proximal kip 470P. A middle portion of the distal insert,between the proximal and distal lips 470P and 470D, has an outer surface473 substantially flush with an outer surface of the distal and proximaltip sections. In some embodiments, the distal and proximal tips sectionsare bonded to the distal insert. The bonding process may involve aswaging/mechanical locking method, precise laser welding, force pressfit, soldering and other means of chemical/mechanical bonding. Theseparate tip design provides a simple assembly process to bond thethermocouple and simplifies cleaning of the device. FIG. 4B alsoillustrates a thermocouple. Thus, according to a method for forming anopen-irrigated catheter tip, a distal lip of a distal insert is insertedin a proximal end of the distal tip section. Mapping electrodes areseated in mapping openings around a circumference of the distal insert.A distal end of a proximal tip section is inserted over a proximal lipof the distal insert. A bonding process is performed to bond the distaland proximal tip sections to the distal insert.

FIGS. 5A-5C illustrate an embodiment of a map and ablate catheter withdistal and proximal irrigation ports. The illustrated embodimentprovides an open-irrigation RF ablation catheter with mapping andablation functions in a Blazer tip platform. The Blazer tip is a tipdeveloped by Boston Scientific. The relatively large surface area of theBlazer tip allows more power to be delivered, which hallows a largerlesion to be made. The larger surface area also promotes increasedpassive cooling by blood over the electrode.

The illustrated catheter has a tip section 526 with distal fluid ports527, and proximal fluid ports 528. The distal insert 529 is made ofplastic components such as Ultem inside the tip which is designed toseparate a proximal reservoir 530 and a distal reservoir 531 fortargeted cooling portions of the tip electrode, provide openings for thecooling fluid and the thermocouple, and provide housing for themicroelectrodes 532 to image real time localized intra cardiac activity.The ends of this distal insert are encapsulated with adhesives tocompletely isolate distal tip chamber from proximal tip chamber.

The cooling lumen 533 is designed to cool the proximal/distal chamberwhile insulating the microelectrode lead wire junction from coolingfluid. The cooling lumen 533 includes several micro holes 534 in theproximal area of the tip to allow fluid to pass through these microholes 534 and through the distal end of the cooling lumen, cooling theproximal tip and ultimately exiting through the proximal tip holes 528.The cooling lumen and tip ports can be configured in different modes tooptimize cooling efficiency for both distal and proximal chamber. Forexample, different diameter sizes and orientations can be implemented toadjust cooling.

Some embodiments include a three microelectrode configuration and someembodiments include a four microelectrode configuration. FIG. 5Cillustrates a distal insert 529 for a four microelectrode configuration.The illustrated insert 529 has openings 536 through which an electricalconnection can be made with the microelectrodes 532. The tip size iswithin a range of approximately 4-10 mm, for example. Some embodimentsdo not include a proximal cooling chamber. The microelectrodes 532,which are used in the mapping function, are isolated from the conductivetip used to perform the ablation using a noise artifact isolator 535.

FIG. 5D illustrates an embodiment of the present subject matterincorporated into a Blazer tip. The illustrated embodiment includes acatheter body 537 and a tip section 526, and includes a plurality ofring electrodes 538, the microelectrodes 532, distal fluid ports 527 andproximal fluid ports 528.

FIGS. 6A-6B illustrate an embodiment of a map and ablate catheter withdistal irrigation ports 627. The cooling lumen 633 includes micro holes634 to pass fluid in a proximal reservoir to cool the proximal portionof the tip. This fluid passes into the distal reservoir out through thedistal fluid ports 627.

Some embodiments shorten the cooling lumen up to the proximal end of thedistal insert, allowing the fluid to cool the proximal end of thechamber before passing the distal tip chamber and ultimately passingthru the distal tip holes. FIGS. 7A-7B illustrate an example of a mapand ablate catheter with distal irrigation ports 727 and a proximalfluid chamber, where fluid exits a cooling lumen into a proximalreservoir 730 before passing into the distal reservoir 731 and exitingthe distal irrigation ports 727.

Electrical signals, such as electrocardiograms (ECGs), are used during acardiac ablation procedure to distinguish viable tissue from not viabletissue. If ECG amplitudes are seen to attenuate during the delivery ofRF energy into the tissue, the delivery of RF energy into that specifictissue may be stopped. However, noise on the ECG signals makes itdifficult to view attenuation. It is currently believed that internalcooling fluid circulation, cooling fluid circulating externally incontact with other electrodes, and/or fluid seepage in between theelectrodes and their housing may cause the noise on this type ofablation catheter.

Various embodiments, as described below, isolate the microelectrodesignal wires from the cooling fluid circulating in the proximal chamberof the hollow ablation electrode, and thus are expected to reduce thenoise that is contributed from the internal cooling fluid circulation.The fluid seal can be provided without bonding or adhesive. Theelectrical components within the tip are isolated from the cooling flowof irrigation fluid while the irrigation fluid maintains internalcooling of the proximal and distal portions of the tip electrode.Further, as provided in more detail below, these designs have thepotential of increasing the accuracy of the temperature readings fromthe thermocouple.

Various distal insert embodiments include design elements configured forself-positioning the distal insert during manufacturing. Theseembodiments reduce the number of processing steps to join the distalinsert to the tip electrode.

FIGS. 8A-8C illustrate various distal insert embodiments configured forself-alignment and configured to isolate electrical components from theirrigation fluid. Some embodiments are configured for self-alignment,some embodiments are configured to isolate electrical components fromthe irrigation fluid, and some embodiments as illustrated are configuredfor both self-alignment and for isolating electrical components from theirrigation fluid. FIG. 8A illustrates a distal insert embodiment withfluid channels formed in a peripheral surface of the insert, FIG. 8Billustrates a distal insert embodiment with fluid lumens formed throughthe distal insert, and FIG. 8C illustrates a section view of the distalinsert embodiment of FIG. 8A.

The illustrated distal inserts 832A and 832B include adistally-extending member 833. The distal insert includes a main bodyportion 834A and 834B and a channel 835 extending from a proximalchannel end 836 through the main body portion to a distal channel end837. The main body portion 834A and 834B has a circumference or outerdiameter generally complementary to an inside diameter of the exteriorwall of the tip section, and has a peripheral surface with openings 838therein sized to receive the electrodes. The exterior wall of the tipsection also has mapping electrode apertures. During assembly, theapertures in the exterior wall and the apertures in the distal insertare aligned, and the mapping electrodes are positioned and potted withinthe apertures. The channel has an interior passage that is isolated fromthe proximal fluid reservoir. Mapping electrode wires extend through theinterior passage of the channel into smaller channels 839 in the mainbody portion of the distal insert to the mapping electrodes.

The distal insert embodiments illustrated in FIGS. 8A-8C include acircumferential groove 840, on which an o-ring is seated to form a sealbetween the distal insert and the exterior wall of the hollow electrodeto prevent fluid from seeping around the side of the distal insert. Thisseal, generally illustrated in FIG. 8C as a seal area, prevents fluidfrom seeping between the distal insert and the exterior wall of the tipsection, and between the electrodes and their housing.

FIGS. 9A-9C illustrate various embodiments for realizing a seal areabetween the distal inserts and the exterior wall of the electrode tip.FIG. 9A generally illustrates the groove 940 and o-ring 941, such as wasgenerally illustrated in FIGS. 8A-8C. Other embodiments include annularor circumferential detents 942 formed as part of the main body andconfigured to extend away from the peripheral surface of the main body,as generally illustrated in FIG. 9B. These detents engage the interiorsurface of the exterior wall of the tip section, thus securing thedistal insert within the tip section. Some embodiments, as generallyillustrated in FIG. 9C, form the peripheral surface with acircumferential gasket 943 configured to provide a seal between thedistal insert and the exterior wall. The gasket 943 may be formed from aflexible material such as a polymer. These embodiments for realizing aseal are not intended to be an exclusive list, as other seals may beused to seal the fluid from the mapping electrodes.

FIG. 10 illustrates a section view of a tip electrode assemblyembodiment 1044 that includes an embodiment of a distal insert 1032. Thedistal insert partitions a hollow ablation electrode into a proximalchamber 1045 and a distal chamber 1046, thus allowing cooling of theproximal chamber 1045. The cooling of the proximal chamber 1045mitigates heating known as “edge effect” before the fluid is directedinto the distal chamber 1046 and discharged through irrigation portsinto the vasculature. The distal insert houses multiple, smallerelectrodes in apertures 1038 in the tip electrode to provide localizedelectrical information.

The illustrated embodiment simplifies and improves the consistency ofthe method for positioning the insert into the hollow tip electrode. Thedistal insert 1032 is inserted into the hollow tip electrode 1044 and isautomatically located within the electrode due to the distally-extendingmember 1033 of the isolation channel. The outer diameter of the insertand the o-ring are designed such that no additional adhesive isnecessary to form a seal between the tip and the distal insert. Theproximal section 1047 of the isolation channel terminates in a slot ofthe adjacent component 1048 that is potted with adhesive.

The exterior wall of the tip section has a distal end 1049 separatedfrom the irrigation ports 1050 of the electrode by a predetermineddistance 1051, and the distally-extending member is configured with apredetermined length 1052 to position the distal insert in the tipsection on a proximal side of the irrigation ports 1050 when the distalchannel end abuts the distal end of the exterior wall of the electrode.

When the apparatus is inserted into a hollow tip electrode in thedirection illustrated by arrow 1053, the distal section of the isolatedchannel has a length that positions the distal edge of the insert aboveor proximal to the irrigation ports, allowing the irrigation portsprovide fluid communication between the distal chamber and the exteriorof the ablation electrode.

The overall diameter of the apparatus is similar enough to the insidediameter of the tip electrode that an o-ring placed in thecircumferential groove provides an adequate seal forcing cooling fluidto flow through the fluid channels 1054, also illustrated in FIG. 8A at854. Because of the design characteristics, manufacturing processes arereduced. The channel houses the thermocouple and signal wires from themicroelectrodes. The proximal end of the insulated channel terminates inthe adjacent structure within the tip, which is potted with epoxy andisolated from the cooling fluid. The thermocouple is in contact with thedistal end of the electrode tip. Some embodiments provide slots 1055 atthe distal channel end of the channel allowing cooling fluid tocirculate into contact with the thermocouple. Some embodiments do notinclude slots, but rather provide a fluid-tight seal between the channeland the distal end of the electrode tip, such that the fluid does notcirculate into contact with the thermocouple.

RF generators are configured with a cut-off temperature, where the RFablation energy is cut off if the temperature reaches a particularlevel. However, some RF generators are configured with a relatively lowcut-off temperature that reflects a less-than-accurate temperaturemeasurement. The slots 1055 are believed to allow the embodiments of thepresent subject matter to operate with such devices. Various embodimentsprovide four slots. Other embodiments include other numbers of slots.Embodiments that include a slotted channel seal the channel at a moreproximate position to prevent fluid from traveling through the channeltoward the wiring. Some embodiments do not include slots, but ratherseal the distal channel end to the distal wall of the electrode toprevent fluid from contacting the thermocouple. Such embodiments thatisolate the thermocouple are believed to provide more accuratetemperature measurements.

The distal insert includes fluid paths from the proximal chamber to thedistal chamber to create a back pressure as fluid enters the proximalchamber, causing the fluid to circulate before being forced through thechannels into the distal chamber. According to various embodiments, thefluid paths have an equal cross-sectional area and equally positionedaround the center of the distal insert. Various embodiments includethree equally-spaced fluid paths. In some embodiments, the fluid pathsare fluid channels 856 formed in a peripheral surface 857 of the mainbody of the distal insert. The fluid channels provide the fluid pathwaystoward the exterior of the distal insert, thus allowing the insert toseat more electrodes around its circumference. In some embodiments, thefluid paths are lumens 858 formed through the main body of the distalinsert. The lumens 858 provide further isolation of the mappingelectrodes from the fluid, as the fluid flowing through the lumens isnot in contact with the interface between the peripheral surface of theinsert and the inner surface of the exterior wall of the electrode.

Wire channel branches, illustrated at 839 in FIG. 8C and at 1039 in FIG.10, allow the signal wires from the microelectrodes to enter theisolated channel. The illustrated embodiment is designed with threeequally-spaced microelectrodes. Thus, the distal electrode embodimentincludes three wire channels extending from an electrode aperture in thedistal insert to the wire channel. According to various embodiments,these channel branches are angled (e.g. 15 to 60 degrees) to aid wirethreading. This entire section is potted with adhesive to isolate thissection from any potential cooling fluid.

FIG. 10 also generally illustrates a method for forming anopen-irrigated catheter tip. A distal insert 1032 is inserted into adistal tip section or hollow electrode 1044. The distal insert includesa distal extension and the distal tip section includes a distal end andirrigation ports separated from the distal end by a predetermineddistance. Inserting the distal insert includes moving the distal insertinto the distal tip section until the distal extension contacts thedistal end of the distal tip section to self-position the distal insertproximate to the irrigation portions. The distal tip section isconnected to a proximally adjacent structure. For example, someembodiments swage the distal tip section to join the distal tip sectionagainst the proximally adjacent structure 1044. The distal insertpartitions the distal tip section into a distal fluid reservoir betweenthe distal insert and the distal end, and a proximal fluid reservoirbetween the distal insert and the proximally adjacent structure. Thedistal insert provides fluid communication between the distal andproximal fluid reservoirs. In various embodiments, inserting the distalinsert into the distal tip section includes aligning mapping electrodeapertures in the distal insert with mapping electrode apertures in thedistal tip section. The mapping electrodes are seated into the mappingelectrode apertures. Wires connected to the mapping electrodes runthrough the channel of the distal insert.

FIG. 11 illustrates an embodiment of a mapping and ablation system 1156that includes an open-irrigated catheter. The illustrated catheterincludes an ablation tip 1157 with mapping microelectrodes 1158 and withirrigation ports 1159. The catheter can be functionally divided intofour regions: the operative distal probe assembly region (e.g. thedistal portion of catheter body 1160), a main catheter region 1161, adeflectable catheter region 1162, and a proximal catheter handle regionwhere a handle assembly 1163 including a handle is attached. A body ofthe catheter includes a cooling fluid lumen and may include othertubular element(s) to provide the desired functionality to the catheter.The addition of metal in the form of a braided mesh layer sandwiched inbetween layers of plastic tubing may be used to increase the rotationalstiffness of the catheter.

The deflectable catheter region 1162 allows the catheter to be steeredthrough the vasculature of the patient and allows the probe assembly tobe accurately placed adjacent the targeted tissue region. A steeringwire (not shown) may be slidably disposed within the catheter body. Thehandle assembly may include a steering member such as a rotatingsteering knob that is rotatably mounted to the handle. Rotationalmovement of the steering knob relative to the handle in a firstdirection may cause a steering wire to move proximally relative to thecatheter body which, in turn, tensions the steering wire, thus pullingand bending the catheter deflectable region into an arc; and rotationalmovement of the steering knob relative to the handle in a seconddirection may cause the steering wire to move distally relative to thecatheter body which, in turn, relaxes the steering wire, thus allowingthe catheter to return toward its form. To assist in the deflection ofthe catheter, the deflectable catheter region may be made of a lowerdurometer plastic than the main catheter region.

The illustrated system 1156 includes an RF generator 1164 used togenerate the energy for the ablation procedure. The RF generator 1164includes a source 1165 for the RF energy and a controller 1166 forcontrolling the timing and the level of the RF energy delivered throughthe tip 1157. The illustrated system 1156 also includes a fluidreservoir and pump 1167 for pumping cooling fluid, such as a saline,through the catheter and out through the irrigation ports 1159. Amapping signal processor 1168 is connected to the electrodes 1158, alsoreferred to herein as microelectrodes. The mapping signal processor 1168and electrodes 1158 detect electrical activity of the heart. Thiselectrical activity is evaluated to analyze an arrhythmia and todetermine where to deliver the ablation energy as a therapy for thearrhythmia. One of ordinary skill in the art will understand that, themodules and other circuitry shown and described herein can beimplemented using software, hardware, and/or firmware. Various disclosedmethods may be implemented as a set of instructions contained on acomputer-accessible medium capable of directing a processor to performthe respective method.

This application is intended to cover adaptations or variations of thepresent subject matter. It is to be understood that the abovedescription is intended to be illustrative, and not restrictive. Thescope of the present subject matter should be determined with referenceto the appended claims, along with the full scope of legal equivalentsto which such claims are entitled.

What is claimed is:
 1. An open-irrigated catheter system for performingmapping and ablation functions, comprising: a tip section having anexterior wall that defines an open interior region within the tipsection, wherein the exterior wall includes a plurality of mappingelectrode openings, wherein at least one of the mapping electrodeopenings is spaced apart from a distal end of the exterior wall of thetip section, wherein the exterior wall includes at least one irrigationport in fluid communication with the open interior, and wherein theexterior wall is conductive for delivering radio frequency (RF) energyfor an RF ablation procedure; a fluid path extending through the tipsection and in fluid communication with the at least one irrigationport; a plurality of mapping electrodes positioned in the mappingelectrode openings in the tip section; at least one insulating elementelectrically insulating the mapping electrodes from the fluid path; anda distal insert positioned within the tip section separating the openinterior region into a distal fluid reservoir and a proximal fluidreservoir, wherein the distal insert has a peripheral surface withopenings therein sized to receive the at least one insulating element.2. The system of claim 1, wherein each mapping electrode has aperipheral surface extending transverse to a longitudinal axis of thetip section, an inner surface facing the open interior region, and anouter surface facing laterally away from the tip section, wherein eachinsulating element covers the peripheral surface and the inner surfaceof its corresponding mapping electrode.
 3. The system of claim 1,wherein the distal insert defines a fluid conduit extending from thedistal fluid reservoir to the proximal fluid reservoir.
 4. The system ofclaim 1, wherein the at least one irrigation port in fluid communicationwith the open interior region includes at least one distal irrigationport in fluid communication with the distal fluid reservoir.
 5. Thesystem of claim 1, wherein the at least one irrigation port in fluidcommunication with the open interior region includes at least oneproximal irrigation port in fluid communication with the proximal fluidreservoir.
 6. The system of claim 1, wherein the at least one irrigationport in fluid communication with the open interior region includes atleast one distal irrigation port in fluid communication with the distalfluid reservoir and at least one proximal irrigation port in fluidcommunication with the proximal fluid reservoir.
 7. The system of claim1, further comprising a fluid cooling lumen extending through the distalinsert to deliver fluid to the distal fluid reservoir, the fluid coolinglumen having a wall with openings therein to deliver fluid to theproximal fluid reservoir.
 8. The system of claim 1, wherein: the tipsection includes a proximal section and a distal section, the proximalsection including a distal side, and the distal section including aproximal side; the distal insert includes a proximal lip on a proximalend of the distal insert and a distal lip on a distal end of the distalinsert; the proximal side of the distal section fits over the distallip; and the distal side of the proximal section fits over the proximallip.
 9. The system of claim 8, wherein the distal insert includes amiddle portion between the proximal and distal lips, the middle portionhaving an outer surface substantially flush with an outer surface of theproximal section and with an outer surface of the distal section. 10.The system of claim 1, wherein: the at least one irrigation port isseparated from the distal end of the exterior wall of the tip section bya predetermined distance; and the distal insert includes adistally-extending member terminating in a distal channel end, whereinthe distally-extending member is configured with a first predeterminedlength to position the distal insert in the tip section on a proximalside of the at least one irrigation port when the distal channel endabuts the distal end of the exterior wall.
 11. The system of claim 1,wherein: the at least one irrigation port is separated from the distalend of the exterior wall of the tip section by a predetermined distance;the distal insert includes a main body portion and a channel extendingfrom a proximal channel end through the main body portion to a distalchannel end, the main body portion having a circumference generallycomplementary to an inner diameter of the exterior wall; the distalchannel end abuts a distal wall of the tip section, the main body ispositioned on a proximal side of the at least one irrigation port, andthe proximal channel end is connected to a proximally adjacentstructure; the channel has an interior passage that is isolated from theproximal fluid reservoir; and the system includes wires extendingthrough the interior passage of the channel into the main body portionof the distal insert to the mapping electrodes.
 12. The system of claim1, further comprising a thermocouple.
 13. The system of claim 1, whereinthe at least one insulating element has a generally annular shape. 14.The system of claim 1, wherein the mapping electrodes include threemapping electrodes approximately equally spaced from each other about acircumference of the tip section.
 15. The system of claim 1, wherein themapping electrodes include four mapping electrodes approximately equallyspaced from each other spaced about a circumference of the tip section.16. An open-irrigated catheter system for performing mapping andablation functions, comprising: a tip section having an exterior wallthat defines an open interior region within the tip section, wherein theexterior wall includes a plurality of mapping electrode openings influid communication with the open interior, wherein at least one of themapping electrode openings is spaced apart from a distal end of theexterior wall of the tip section, wherein the exterior wall includes atleast one irrigation port in fluid communication with the open interiorregion and wherein the exterior wall is conductive for delivering radiofrequency (RF) energy for an RF ablation procedure; a fluid pathextending through the tip section and in fluid communication with the atleast one irrigation port; a plurality of mapping electrodes positionedin the mapping electrode openings in the tip section, wherein eachmapping electrode has a peripheral surface extending transverse to alongitudinal axis of the tip section, an inner surface facing theinterior of the tip section, and an outer surface facing laterally awayfrom the tip section; and at least one insulating element electricallyinsulating the mapping electrodes from the fluid path, wherein eachinsulating element covers the peripheral surface and the inner surfaceof its corresponding mapping electrode.
 17. The system of claim 16,further comprising a distal insert positioned within the tip sectionseparating the open interior region into a distal fluid reservoir and aproximal fluid reservoir, wherein the distal insert has a peripheralsurface with openings therein sized to receive the at least oneinsulating element.
 18. The system of claim 16, wherein the insulatingelements extend outward from the exterior wall past an outside surfaceof the mapping electrodes.
 19. An open-irrigated catheter system forperforming mapping and ablation functions, comprising: a tip sectionhaving an exterior wall that defines an open interior region within thetip section, wherein the exterior wall includes at least three mappingelectrode openings and at least one irrigation port in fluidcommunication with the open interior region, wherein the exterior wallis conductive for delivering radio frequency (RF) energy for an RFablation procedure; at least three mapping electrodes positioned in theat least three mapping electrode openings; at least three insulatingelements surrounding the at least three mapping electrodes; and a distalinsert positioned within the tip section and separating the openinterior region into a distal fluid reservoir and a proximal fluidreservoir, the distal insert defining a fluid conduit extending from thedistal fluid reservoir to the proximal fluid reservoir, the distalinsert having a peripheral surface with openings therein sized toreceive the insulating elements, wherein the insulating elementselectrically insulate the mapping electrodes from the distal insert,wherein at least one of the irrigation ports is in fluid communicationwith the distal fluid reservoir.
 20. The system of claim 19, wherein atleast one of the irrigation ports is in fluid communication with theproximal fluid reservoir.